Curable, styrene-containing resin compositions having reduced styrene emissions

ABSTRACT

This invention relates to free-radical curable, styrene-containing resin compositions having reduced styrene emissions. More particularly, the invention relates to free-radical curable, styrene-containing resin compositions having reduced styrene emissions comprising: (a) a polymerizable alpha, beta-ethylenically unsaturated carboxylate resin, which is dissolved in styrene; (b) a paraffin wax; and (c) a fluorocarbon surfactant.

This invention relates to thermoset resins. More particularly, thisinvention relates to free-radical curable, styrene-containing resincompositions.

BACKGROUND OF THE INVENTION

Free-radical curable, styrene-containing resins are well-known to thoseskilled in the art and widely available from commercial sources. Suchresins include, for example, styrene-containing unsaturated polyesters,vinyl esters and urethane acrylates or methacrylates. All of theseresins are alpha, beta-ethylenically unsaturated carboxylates. Theseresins, especially unsaturated polyesters, can be easily adapted to manycommon thermoset molding techniques for the construction andtransportation industries, including the manufacture of parts forautomobiles, trucks, boats, machine housings and household items such asbath fixtures. Another application for such resins is in theconstruction of tanks, piping and process equipment for chemicals andchemical waste such as underground gasoline storage tanks. These resinsare selected as a replacement for metals such as steel, stainless steel,aluminum and bronze because of their ability to resist corrosion andchemical attack. Therefore, it is desirable to provide such resinswhich, when molded, have good toughness, impact and adhesion propertiesas well as hydrolytic, thermal and chemical resistance.

However, styrene emissions associated with the manufacture offree-radical curable, styrene-containing resins are now limited byregulations promulgated in 1989 by the U.S. Occupational Safety andHealth Administration (OSHA). According to these regulations,manufacturers in many industries must reduce workplace styrene emissionsfrom 100 parts per million to 50 parts per million. Environmentalrequirements issued by the South Coast Air Quality Management District(SCAOMD) in California apply to such resins and mandate that styreneemissions must be less than 60 grams per square meter of styrene by apaint can lid test described below.

In order to meet new environmental regulations, manufacturers ofstyrene-containing resins might either reduce the styrene monomercontent of resins or suppress emissions from existing styrene-containingcompositions. The problem with lowering the styrene content is thatstyrene functions to provide a workable viscosity of the resin and tocrosslink with the unsaturation in the resin, such as a polyesterpolymer backbone. Therefore, lowering the amount of styrene in the resinwill have an impact on other properties.

Several approaches to lowering styrene emissions have been testedwithout success. One approach is to lower the molecular weight of theresin in order to reduce the amount of styrene needed to obtain aworkable resin viscosity. The problem with this approach is that theflexural strength of the resin is greatly decreased, particularly whentested after exposure to high temperatures or chemical exposure. Anotherapproach to reducing emissions in unsaturated polyester resins is tosubstitute part of the styrene with another additive such ashydroxyethyl methacrylate or methyl methacrylate. However, neither ofthese substitutes works as well as styrene in most applications. Forexample, chemical resistance of a polyester resin is lower in ahydroxyethyl methacrylate additive system. Similarly, vinyl toluene hasbeen tested as a substitute for styrene in unsaturated polyesters. Whileit appeared that the styrene emissions and interlaminar adhesion wereacceptable, this system could not be used at workable viscosity levelswhich would also meet styrene emission requirements.

The general object of this invention is to provide free-radical curable,styrene-containing resin compositions having reduced styrene emissions.It is another object of the invention to provide such resins withreduced styrene emissions without significantly affecting thepreparation, processing and physical properties of the resins when usedin molding processes. It is another object to provide a simple,inexpensive method for making such resin compositions. It is yet anotherobject to provide molded articles having good physical properties whichare made from such compositions. Other objects appear hereinafter.

These and other objects are achieved by the addition of a small amountof a paraffin wax and a fluorocarbon surfactant to a free-radicalcurable, styrene-containing polymerizable resin composition.Unexpectedly, it has been found that compositions containing a paraffinwax and a fluorocarbon surfactant have lower styrene emissions withoutsignificantly affecting preparation, processing, and physicalproperties, particularly chemical and hydrolytic resistance andinterlaminar adhesion of the cured or polymerized resin compositions.

SUMMARY OF THE INVENTION

The invention is a free-radical curable, styrene-containing resincomposition having reduced styrene emissions comprising:

(a) a polymerizable alpha, beta-ethylenically unsaturated carboxylateresin, which is dissolved in styrene;

(b) a paraffin wax; and

(c) a fluorocarbon surfactant;

wherein said paraffin wax and said fluorocarbon surfactant are providedin amounts sufficient to reduce said styrene emissions withoutsignificantly affecting physical properties of said resin compositions,such as interlaminar adhesion and hydrolytic and chemical resistance.

In a preferred embodiment, the resin composition of the inventioncomprises about 0.05 to about 0.3 wt. % paraffin wax, and preferablyabout 0.1 to about 0.2 wt. % paraffin wax. In another preferredembodiment, the concentration of the fluorocarbon surfactant comprisesabout 0.001 to about 0.1 wt. % fluorocarbon surfactant, and preferablyabout 0.005 to about 0.09 wt. % fluorocarbon surfactant. The inventionalso comprises methods for making such improved resin compositions. In apreferred method, the unsaturated polymerizable resin dissolved instyrene is mixed with the paraffin wax and the fluorocarbon surfactant.

DETAILED DESCRIPTION OF THE INVENTION

This invention applies to free-radical curable resin compositionscontaining styrene. As used herein, the term "free-radical curable,styrene-containing resins" means liquid resin compositions containingstyrene which are transformed from a liquid to a gel or solid state atthe time of molding or casting by crosslinking viafree-radical-initiated vinyl addition polymerization. For example,crosslinking of reactive sites in styrene-containing unsaturatedpolyester resins occurs via vinyl addition polymerization ofethylenically unsaturated styrene monomer and the alpha, betaolefinically unsaturated moieties of the polyester.

Examples of free-radical curable, styrene-containing resin compositionsto which the invention applies are styrene-containing unsaturatedpolyesters, vinyl esters and urethane acrylates and methacrylates. Theseresins are widely commercially available and well known to those skilledin the art.

Unsaturated polyester resins useful in the invention may be oligomersobtained by the condensation reaction of at least one unsaturated di- orpolycarboxylic acid or anhydride with at least one di- or polyhydricalcohol, and, preferably, at least one saturated or aromatic di- orpolycarboxylic acid or anhydride. Typical unsaturated di- orpolycarboxylic acids or anhydrides include maleic acid, fumaric acid,citaconic acid, chloromaleic acid, allyl succinic acid, itaconic acid,mesaconic acid, their anhydrides and mixtures thereof, with maleicanhydride being the preferred choice. Examples of di- or polyhydricalcohols which are useful in the invention include neopentyl glycol,ethylene glycol, diethylene glycol, triethylene glycol, propyleneglycol, dipropylene glycol, 1,4-butanediol, polyethylene glycol,mannitol, 1,2-propanediol, 1,6-hexanediol, 1,3-butylene glycol andmixtures thereof, with propylene glycol being preferred. Typical di- orpolycarboxylic acids include isophthalic acid, orthophthalic acid,terephthalic acid, succinic acid, adipic acid, chlorendic anhydride andmixtures thereof, with isophthalic acid being the preferred choice.Typical molecular weights of unsaturated polyesters (on a solid basis)useful in the instant invention are between about 1000 and about 2500g/mole. The polyesters typically are dissolved in about 20-60 wt. %styrene monomer solution which usually contain polymerizationinhibitors. Most preferred are unsaturated polyesters based onisophthalic acid, maleic anhydride and propylene glycol dissolved inabout 30-50 wt. % styrene.

Vinyl ester resins useful in the invention are produced by the additionof an ethylenically unsaturated monocarboxylic acid to a backbone(usually epoxy-containing) producing terminal unsaturation and which canbe cured with vinyl monomers similar to those used for crosslinkingpolyesters. Various epoxy resins are used, including the diglycidylother of bisphenol A, or higher homologues thereof, the diglycidyl etherof tetrabromo bisphenol A, epoxylated phenol-formaldehyde novolac andpolypropylene oxide diepoxide. The most commonly used acids are acrylicand methacrylic acids. The acid-epoxide reaction is straightforward andis catalyzed by tertiary amines, phosphines, alkalis or onium salts. Theacid-epoxide reaction results in pendant hydroxyl groups which provideadhesion and/or reactive sites for further modification with compoundssuch as anhydrides or isocyanates. Vinyl ester resins are diluted with areactive monomer such as styrene usually containing inhibitors. Vinylester resins useful in the invention are described in more detail byAnderson and Messick in Developments in Reinforced Plastics--1, pp.29-57, Edited by G. Pritchard, Applied Science Publishers Ltd., London,1980, which is incorporated by reference herein. One preferred vinylester resin useful in the invention is sold under the trademark Derakane470 by The Dow Chemical Company, Midland, Mich. This resin is an epoxynovolac vinyl ester resin for high-temperature applications which has anepoxy resin based on phenol-formaldehyde novolac incorporated into thevinyl ester resin backbone, increasing the crosslink density when theresin is cured.

The urethane acrylate and methacrylate resins useful in the inventionmay be made by the reaction of a di- or polyisocyanate and ahydroxyalkyl acrylate or methacrylate with a di- or polyhydric alcohol.Examples of these resins are contained in U.S. Pat. No. 4,480,079 and inEuropean Patent Application 86303822.0, which are incorporated byreference herein. In U.S. Pat. No. 4,480,079, there are describedpolyurethane polyacrylate or polymethacrylate resins derived from ahydroxyalkyl acrylate or methacrylate by reaction of hydroxyl groupsthereof with the isocyanate groups of (i) a polyisocyanate free fromurethane groups and having an isocyanate functionality greater than 2.0or (ii) a urethane polyisocyanate derived from a polyisocyanate byreaction thereof with the hydroxyl groups of an aliphatic alcohol havingup to 3 hydroxyl groups, the urethane polyisocyanate having anisocyanate functionality greater than 2.0. The described urethaneacrylates are copolymerizable with a vinyl monomer which is methylmethacrylate, but these resins may also be dissolved in styrenecontaining at least one inhibitor.

The ethylenically unsaturated styrene monomers which may be used in thecurable resins of the invention can be any ethylenically unsaturatedstyrene monomer capable of cross-linking the unsaturation in the resinvia vinyl addition polymerization. The preferred monomer is styrenebecause it provides an economical monomer solution, is a good solventfor unsaturated resins and enables low viscosity at lower monomerlevels.

The paraffin waxes which are useful in the invention include those withmelting points between about 50°-700° C. (120°-1600° F.). One preferredparaffin wax is Eskar R-45 available from Amoco Oil Company, Chicago,Ill. This paraffin wax has a melting point of about 600° C. (1400° F.).The paraffin wax is added in an effective amount to reduce styreneemissions while preferably maintaining acceptable adhesion properties inthe cured resin composition. The preferred concentration of paraffin waxis about 0.05 to about 0.3 wt. % of the total resinous components (i.e.,resin and styrene monomer). It has been found that at paraffin levelsbelow about 0.05 wt. %, styrene emissions were too high, and at levelsabove about 0.3 wt. %, adhesion properties of the resin composition,i.e., ability of individual layers of the resin composition to adhere toone another, were unacceptable. A most preferred concentration ofparaffin wax is about 0.1 to about 0.2 wt. %, with the optimum preferredconcentration being about 0.15 wt. % paraffin wax.

The fluorocarbon surfactants useful in the invention are preferablynonionic, ethoxylated fluorocarbons. Most preferred are fluorocarbonsurfactants sold under the trademark Zonyl® FSN and Zonyl FSN-100 by E.I. DuPont, Wilmington, Del. These fluorocarbon surfactants are describedin more detail in DuPont Bulletin E-95556, December, 1988, and DuPontBulletin H-00172, August, 1988, both of which are incorporated byreference herein. These fluorocarbon surfactants are of the formulaR_(f) CH₂ CH₂ O(CH₂ CH₂ O)_(x) H, wherein R_(f) =F(CF₂ CF₂)₃₋₈, andwherein x can be about 1-20. The fluorocarbon surfactant is added, incombination with the paraffin wax, in an effective amount sufficient toreduce styrene emissions while preferably maintaining acceptableadhesion properties in the cured resin composition. The preferredconcentration of fluorocarbon surfactants useful in the invention isabout 0.001 to about 0.1 wt. % of the total resinous components (i.e.,resin and styrene monomer). At concentrations which are higher thanabout 0.1 wt. %, the adhesion properties of the resin were good, but thestyrene emissions were too high. Below 0.001 wt. % fluorocarbonsurfactant, the styrene emissions were satisfactory, but the adhesionproperties of the resin were unacceptable. A most preferredconcentration of fluorocarbon surfactant is about 0.005 to about 0.09wt. %, with the optimum preferred concentration being about 0.01 wt. %.

Optionally, other additives such as catalysts, fibers, fillers,pigments, mold release agents, water scavengers, internal lubricants,low profile additives and other processing aids, all of which arewell-known to those skilled in the art, can be added to the free-radicalcurable resin compositions of the invention. Preferably, a peroxidecatalyst such as methylethylketone peroxide is used to catalyze thecrosslinking of the resin and styrene monomer. Also, small amounts oforganic cobalt initiators are preferably added to facilitate thecatalyst breakdown.

Typically, in making the improved curable resin compositions accordingto the invention, a resin, such as an unsaturated polyester, vinyl resinor urethane acrylate, described above, is dissolved in styrene monomer.Next, an effective amount of paraffin wax and fluorocarbon surfactantare mixed together with the styrene-containing composition. The additionof paraffin wax and fluorocarbon surfactant can be made at the time ofpreparing the resin, which is preferred, or just prior to use by theresin end-user. The liquid resin is then used in a free-radical curedmolding process such as hand lay-up, spray-up or other reactive moldingprocesses to form useful molded products.

The invention described herein is illustrated, but not limited, by thefollowing examples.

EXAMPLES EXAMPLE 1 Unsaturated Polyester Resins Prepared with ParaffinWax and Fluorocarbon Surfactant

This example shows the preparation of an unsaturated polyester resincomposition according to the invention.

An unsaturated polyester comprising equal molar parts of isophthalicacid and maleic anhydride with 10 mole percent excess propylene glycolwas prepared according to the formulation shown in Table 1. Thispolyester resin formulation is described in Amoco Chemical CompanyBulletins, isophthalic Acid, Bulletins IP-43b and IP-86a, available fromAmoco Chemical Company, Chicago, Ill., which are incorporated herein byreference.

                  TABLE 1                                                         ______________________________________                                        Formulation of Unsaturated Polyester Resin                                                   Mole ratio                                                                            Wt. %                                                  ______________________________________                                        Propylene Glycol 2.20      44.3                                               Isophthalic Acid 1.00      44.0                                               Maleic Anhydride 1.00      26.0                                               less 1st stage water                                                                           -2.00     -9.5                                               less 2nd stage water                                                                           -1.00     -4.8                                               Yield            --        100.0                                              Styrene Monomer  --        100.0                                              ______________________________________                                    

The resin was processed using a two-stage method in a stirred heatedbatch reactor with a partial condenser and a total condenser. In thefirst stage, propylene glycol and isophthalic acid were charged to thereactor and heated to a maximum of 205° C. (400° F.) and reacted to anacid number less than 10. This prepolymer was then cooled to below 160°C. (325° F.) and the glycol loss was measured. Any loss was made up bythe addition of propylene glycol.

In the second stage, maleic anhydride was charged to the reactor, heatedto a maximum temperature of 230° C. (450° F.) and reacted to an acidnumber less than 10 and a Gardner-Holdt viscosity of V-X based on 60%nonvolatile material (NVM).

The polymerization mixture was then cooled to 205° C. (400° F.), and 150ppm hydroquinone was added to inhibit the resin. The resin was hotblended at a temperature of about 160°-175° C. (325°-350° F.) to 50% NVMwith styrene inhibited with 75 ppm (based on resin solids)p-benzoquinone. The properties of the resin are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Properties of Unsaturated Polyester Resin                                     ______________________________________                                        Non-volatile Material, wt. %                                                                        50.49                                                   Gardner-Holdt Viscosity                                                                             N-O                                                     Brookfield Viscosity at 25° C., cP                                                           445                                                     Gardner Color         7-                                                      Hydroxyl Number (Solid)                                                                             38.3                                                    Acid Number (solid), mg KOH/g                                                                       9.5                                                     SPI Gel Test, 1% benzoyl peroxide                                             at 82° C.                                                              Gel Time, min:sec     5:11                                                    Cure Time, min:sec    7:48                                                    Peak Exotherm         239° C. (398° F.)                         Styrene Emissions (By SCAQMD)                                                                       120-140 g/sq meter                                      Interlaminar Adhesion Excellent                                               ______________________________________                                    

Next, 0.15 wt. % of a paraffin wax, melting point 600° C., availablefrom Amoco Oil Company, Chicago, Ill. under the trademark Eskar R-45,was added to the above-described unsaturated polyester resin by firstdissolving the wax in an equal amount of styrene (50:50 wt./Wt.), whilewarming to about 40° C., and then adding the wax in styrene to theunsaturated polyester resin at room temperature. interlaminar adhesionof the resin formulation with the addition of wax, but without thefluorocarbon surfactant, was poor.

Next, 0.01 wt. % of a fluorocarbon surfactant, available from E. I.DuPont, Wilmington, Del. under the trademark Zonyl FSN, was added to thepolyester resin at room temperature. The formulation and results ofstyrene emissions and adhesion testing of this improved resin system areshown in Table 3.

The SCAQMD method of testing styrene emissions is issued by the SouthCoast Air Quality Management District, in the State of California and isa "paint can lid" test. Briefly, the SCAQMD method is a standard methodfor static volatile emissions which determines the % weight loss definedas % volatile emission of a polyester resin during its polymerization togel under the condition of the test. Briefly, a sample of theunpolymerized resin is weighed onto a suitable container, preferably agallon can lid of 14.5 cm diameter, from a triple tight can and allowedto stand for 30 minutes with weights being measured at intervals. Theresin is catalyzed with an appropriate peroxide catalyst, such asmethylethylketone peroxide, and the rate of loss and volatile emissionsare then calculated. A sample of the polymerized form of the same resinis then weighed onto a suitable container with a paper clip added andallowed to stand until the sample has gelled with weights being measuredat intervals. The rate of loss and volatile emissions are thencalculated. The detailed procedure and calculations are available fromthe South Coast Air Quality Management District, Los Angeles, Calif.,under the title "Standard Method for Static Volatile Emissions", revisedSep. 3, 1987, which is incorporated herein by reference. The acceptablelimit for styrene emissions according to the South Coast Air QualityManagement District is below 60 g/sq meter.

The interlaminar adhesion test procedure is as follows. A laminate ofthe resin is prepared and allowed to cure for 24 hours at roomtemperature. One-third of the cured resin is covered with Mylar, and asecond laminate is applied and cured for 24 hours at room temperature.The completed laminate is post cured for two hours at 100° C. It is thencut into 4-inch wide sections, with the top third of each sectioncontaining the Mylar. The layers are separated and the surfaces arejudged for adhesion by visual assessment of fiber tear. One hundredpercent (100%) fiber tear is viewed as excellent adhesion, whereas 25%fiber tear is considered to be poor.

                  TABLE 3                                                         ______________________________________                                        Unsaturated Polyester/Paraffin Wax/Fluorocarbon Surfactant                    Resin System Formulation And Properties                                       Reactants                Wt. %                                                ______________________________________                                        Polyester Resin (50 NVM in Styrene)                                                                    100.00                                               (1.0 M/1.0 M/2.20 M - MAN/IPA/PG,                                             Eq. Wt. 2300)                                                                 Paraffin Wax              0.15                                                Fluorocarbon Surfactant   0.01                                                Cobalt Initiator (6 wt. % Cobalt)                                                                       0.3                                                 Methylethylketone Peroxide (MEKP) Catalyst                                                              1.0                                                 Properties                                                                    Styrene Emissions (By SCAQMD)                                                                          22 g/sq meter                                        Interlaminar Adhesion    Excellent                                            ______________________________________                                         MAN = maleic anhydride                                                        IPA = isophthalic acid                                                        PG = propylene glycol                                                    

The small amounts of paraffin wax and fluorocarbon surfactant reducestyrene emissions without significantly affecting important physicalproperties such as interlaminar adhesion. A comparison of physicalproperties of an isopolyester resin made as described above, except that1 wt. % benzoyl peroxide was used as catalyst, with and without theaddition of a paraffin wax and fluorocarbon surfactant, are shown inTable 4. Cure conditions for the clear castings were as follows: 16 hrsat 57° C. (135° F.), 1 hr at 82° C. (180° F.), 1 hr at 104° C. (220°F.), 1 hr at 120° C. (248° F.).

                  TABLE 4                                                         ______________________________________                                        Resin Formulation                                                                             Control (wt. %)                                                                            Sample (wt. %)                                   ______________________________________                                        Polyester Resin (See                                                                          100.0        100.0                                            Table 3)                                                                      Paraffin Wax    0             0.15                                            Fluorocarbon Surfactant                                                                       0             0.01                                            Methylethylketone Peroxide                                                                    1.0           1.0                                             ______________________________________                                        Liquid Resin Properties                                                                       Control      Sample                                           ______________________________________                                        NVM %           50           50                                               Styrene Emissions, gm/sq                                                                      127          34                                               meter (by SCAQMD)                                                             ______________________________________                                        Physical Properties of Clear Castings                                                         Control      Sample                                           ______________________________________                                        Flex Modulus, 10 × 6 psi                                                                .520 (.013)  .509 (.007)                                      Flex Strength, 10 × 3 psi                                                               15692 (1206) 14904 (1200)                                     Tensile Modulus, 10 × 6 psi                                                             .553 (.093)  .540 (.024)                                      Tensile Strength, 10 × 3 psi                                                            9948 (989)   9553 (746)                                       Tensile Elongation, %                                                                         2.3          2.1                                              ______________________________________                                        6 Day (144 hrs) Water Boil Test                                                               Control      Sample                                           ______________________________________                                        Flex Modulus, 10 × 6 psi                                                                .447 (.012)  .454 (.011)                                      Flex Strength, 10 × 3 psi                                                               12566 (582)  10942 (926)                                      Flex Modulus, % retained                                                                      86.0         89.0                                             Flex Strength, % retained                                                                     80.0         76.0                                             Weight Gain, %  1.053        1.021                                            ______________________________________                                    

Flexural modulus and flexural strength were tested by ASTM method D 790.Tensile modulus, tensile strength and tensile elongation were tested byASTM method D 638. The water boil method is as follows. The resin sampleis placed in boiling water reflux at 100° C. for 6 days and then removedand tested for physical properties.

Table 4 demonstrates physical properties of resins made according to theinvention are not significantly affected by addition of the paraffin waxand fluorocarbon surfactant.

EXAMPLE 2 Orthopolyester and Vinyl Ester Resins Prepared with ParaffinWax and Fluorocarbon Surfactant

Other examples of free-radical curable, styrene-containing resincompositions useful in the instant invention are an orthopolyester resindesignated 1060-5, available from Reichhold Chemical, Jacksonville,Fla., and a vinyl ester resin designated Derakane 470 available from DowChemical Company, Midland, Mich. These resins have styrene emissions of98 g/sq. meter and 110 g/sq. meter, respectively, before addition of theparaffin wax and fluorocarbon surfactant. The paraffin wax (0.15 wt. %)and fluorocarbon surfactant (0.01 wt. %) were added to these resins asdescribed above to achieve reduced styrene emissions while maintaininggood adhesion properties. The results of styrene suppression andadhesion testing for these resins are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Free-Radical Styrene-Containing Curable Resin System                          Formulation And Properties                                                    ______________________________________                                                               Wt. %                                                  ______________________________________                                        Reactants                                                                     Reichhold 1060-5 Resin (50 NVM in Styrene)                                                             100.0                                                Paraffin Wax              0.15                                                Fluorocarbon Surfactant   0.01                                                Methylethylketone Peroxide Catalyst                                                                     1.0                                                 Properties                                                                    Styrene Emissions (By SCAQMD)                                                                          40 g/sq meter                                        Interlaminar Adhesion    Excellent                                            Reactants                                                                     Derakane 470 Resin (50 NVM in Styrene)                                                                 100.0                                                Paraffin Wax              0.15                                                Fluorocarbon Surfactant   0.01                                                Methylethylketone Peroxide Catalyst                                                                     1.0                                                 Properties                                                                    Styrene Emissions (By SCAQMD)                                                                          47 g/sq meter                                        Interlaminar Adhesion    Excellent                                            ______________________________________                                    

The free-radical curable styrene-containing resin compositions madeaccording to the invention have many advantages. First, the resins ofthe invention have reduced styrene emissions to meet new environmentalstandards. Second, the resins have good physical properties includingtoughness, impact strength, interlaminar adhesion and chemicalresistance. Third, they enable a formulation which is simple andinexpensive to process.

This invention has been described in terms of specific embodiments setforth in detail. It should be understood, however, that theseembodiments are presented by way of illustration only, and that theinvention is not necessarily limited thereto. Modifications andvariations within the spirit and scope of the claims that follow will bereadily apparent from this disclosure, as those skilled in the art willappreciate.

That which is claimed is:
 1. A method for making a free-radical curable,styrene-containing resin composition having reduced styrene emissionsreacting a polymerizable alpha, beta-ethylenically unsaturatedcarboxylate resin, which is dissolved in styrene, with(a) from about0.05 wt. % to about 0.3 wt. % paraffin wax; and (b) from about 0.001 wt.% to about 0.1 wt. % fluorocarbon surfactant.
 2. The method of claim 1wherein the polymerizable alpha, beta-ethylenically unsaturatedcarboxylate resin comprises an unsaturated polyester.
 3. The resincomposition of claim 1 wherein the polymerizable alpha,beta-ethylenically unsaturated carboxylate resin comprises a vinylester.
 4. The resin composition of claim 1 wherein the polymerizablealpha, beta-ethylenically unsaturated carboxylate resin comprises aurethane acrylate or methacrylate.
 5. The resin composition of claim 1wherein the fluorocarbon surfactant comprises a nonionic, ethoxylatedfluorine compound.
 6. The resin composition of claim 1 wherein thepolymerizable alpha, beta-ethylenically unsaturated carboxylate resin isan unsaturated polyester.
 7. The resin composition of claim 6 whereinthe unsaturated polyester comprises an oligomer obtained by thecondensation reaction of at least one unsaturated di- or polycarboxylicacid or anhydride with at least one di- or polyhydric alcohol, and atleast one saturated or aromatic di- or polycarboxylic acid or anhydride.8. The resin composition of claim 7 wherein the unsaturated di- orpolycarboxylic acid or anhydride comprises maleic anhydride, the di- orpolyhydric alcohol comprises propylene glycol, and the saturated oraromatic di- or polycarboxylic acid or anhydride comprises isophthalicacid.